Abstract
Purpose: :
Retinal ganglion cells (RGC) are vital for conveying information from the neuroretina. Hypoxia induced apoptosis is responsible for reducing RGC viability in chronic ocular disorders. Sirtuin 1 (SIRT1) is important for preserving cell viability during hypoxia. We will investigate SIRT1’s role in sustaining RGC viability during hypoxia.
Methods: :
Differentiated RGCs (RGC-5) using staurosphorine received varying hypoxic concentrations (100-500 µM) of cobalt chloride (CoCl2) for 24hrs. Hypoxia induced cell viability was assessed by WST-1 assay. SIRT1’s role in promoting viability was determined indirectly via sirtinol (SIRT1 inhibitor). Hypoxia induced apoptosis was evaluated by measuring stress activated protein kinase/c-JUN N-terminal kinase (SAPK/JNK) and caspase 3 activity.
Results: :
CoCl2 concentrations greater than 200 µM resulted in significantly reduced RGC viability (p = 0.01). SIRT1 levels increased significantly (p < 0.01) during CoCl2 treatment: 100 (6.5-fold), 200 (6-fold), 300 (3.5-fold), and 400 µM (4.5-fold). Phosphorylated SAPK/JNK increased 36-fold (200 µM CoCl2 concentration), then plateaued at the 300 (25-fold) and 400 (27.8-fold) µM CoCl2 concentrations (p < 0.01). Caspase 3 activity increased with CoCl2 and sirtinol (p < 0.05) treatment. Sirtinol reduced RGC viability and SIRT1 levels (p < 0.01) while having higher effect on SAPK/JNK phosphorylation.
Conclusions: :
SIRT1 significantly influences RGC viability. Sirtinol’s effect reflects the interaction SIRT1 has with apoptotic signaling proteins. This investigation demonstrated SIRT1 importance in forestalling the effects of hypoxia induced apoptosis.
Keywords: ganglion cells • hypoxia